Noise vs performance

[estutjaweh]

Don't know if that title is actually correct but here goes anyway.

I keep hearing lots about the benefits of removing Pre-cats. Doing so seems to reduce under bonnet heat and also free up a few extra little ponies by minimizing air flow resistance.

My problem is that I already have an act cherry bomb exhaust fitted and removing the pre-cats as well would result in being way too loud for the authorities here in Germany so heres my question...What would make more sense on the whole:

1 - replace ACT with standard exhaust and remove pre-cats
2 - keep ACT system and leave pre-cats in place
3 - ?

[Sardonicus]

Removing pre-cats makes next to no difference to the noise out the back of the exhaust IMO it just makes the manifolds ring/metallic sound a little

[rigga]

Agreed, the smaller precats before the main dustbin cat if removed won't make that much difference to sound levels.,removing the main large cat on the other hand will.

[phazed]

Main cat in, 94 DB

Main cat removed, 100 DB or there abouts.

This is with a standard system.

[rigga]

phazed said:

Main cat in, 94 DB

Main cat removed, 100 DB or there abouts.

This is with a standard system.

All expotential I believe though peter, so a 6 DB rise is a lot lot louder than it suggests

[phazed]

True!

That's why I put my inserts in for distances.

[Alun450]

I'm undecided, I've got a y piece de catted but feel it's going to be to loud for the locals! The best sounding to my ears was a 4.0 with half perforated silencer, just right.

Just got back from Chatsworth, they all sound quiet in a field!

I'm starting to think I don't need the extra hp from de catted pipe as 90% of the time I cant use it anyway. My car feels loud now! Saying that I used to be un decided now I'm not so sure!!!

[SILICONEKID350HP]

Alun450 said:

I'm undecided, I've got a y piece de catted but feel it's going to be to loud for the locals! The best sounding to my ears was a 4.0 with half perforated silencer, just right.

Just got back from Chatsworth, they all sound quiet in a field!

I'm starting to think I don't need the extra hp from de catted pipe as 90% of the time I cant use it anyway. My car feels loud now! Saying that I used to be un decided now I'm not so sure!!!

I did not see you ..where were you parked ..I prefer the ACT decat ,pre cats out and standard exhaust ..

[Goaty Bill]

phazed said:

True!

That's why I put my inserts in for distances.

And you claim to be a dedicated member of MCC? Ha!

[Alun450]

Wuss, lol. Daz I didn't know what to do ask everybody! I was with the grandson parked between J.Agger and Johns orange Chim, had my bonet open, went off looking most the time. Had a chat with Alex.

Re pipes, standard sounds the best in my book.... Well it doesn't but it does when having to live with it!

[chris1972]

Where do you get the inserts from? My exhaust is already sleeved and I've just taken the pre-cats out, plus will be removing the main cat. Inserts may be a good choice for early starts and I gather my intended system will be a little loud

[phazed]

ACT I believe but check with Daz as I bought mine S/H.

[SILICONEKID350HP]

chris1972 said:

Where do you get the inserts from? My exhaust is already sleeved and I've just taken the pre-cats out, plus will be removing the main cat. Inserts may be a good choice for early starts and I gather my intended system will be a little loud

Got mine from V8 Monster ..sometimes advertises them on fleabay

[chris1972]

SILICONEKID350HP said:

Got mine from V8 Monster ..sometimes advertises them on fleabay

Thanks for that!

[Chilliman]

Pre-cats out, Act decat Y, standard box.... quiet enough when pootling, wrath of the Gods when not

[900T-R]

same-ish here - ACT manifolds with decat pipes and OEM exhaust system. Sounds just right to these ears:

http://www.youtube.com/watch?v=Kpc8CPDNd24&lis...

[Sardonicus]

Chilliman said:

Pre-cats out, Act decat Y, standard box.... quiet enough when pootling, wrath of the Gods when not

Spot on

[chris1972]

Means me re-sleeving the silencer... can't bring myself to add more work to my list at the moment!

[TV8]

ACT Y piece and Cherry bomb system but pre-cats are still in. I think that the pre-cats out give noise that is more noticeable to the driver. From inside the car, I think my car is relatively quiet. Those that follow me down the road say otherwise!

http://www.youtube.com/watch?v=fzQ2U2eN9Bg

[Northernchimp]

I phoned an alleged performance car place today about this. He said:

"Why would you want to destroy your engine? The manufacturer of your vehicle has spent millions of pounds...blah blah"

Sounded like a right Keith. Long story short, to save me from myself he wouldn't do it. Has put me off a bit, though I dont see how it will destroy my engine.